AUTHOR=Takada Kaho , Chiba Tomoki , Miyazaki Takayuki , Yagasaki Lisa , Nakamichi Ryo , Iwata Takanori , Moriyama Keiji , Harada Hiroyuki , Asahara Hiroshi 

TITLE=Single Cell RNA Sequencing Reveals Critical Functions of Mkx in Periodontal Ligament Homeostasis

JOURNAL=Frontiers in Cell and Developmental Biology

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/cell-and-developmental-biology/articles/10.3389/fcell.2022.795441

DOI=10.3389/fcell.2022.795441

ISSN=2296-634X

ABSTRACT=<p>The periodontal ligament (PDL) comprises a fibrous tissue that connects teeth to alveolar bone and is essential for periodontal function. The transcription factor mohawk homeobox (<italic>Mkx</italic>) is expressed in the PDL where it plays an important role in the development and maintenance of the PDL. However, the precise and critical functions of <italic>Mkx</italic> in the cell populations comprising PDL have not yet been elucidated. The present study aimed to clarify the effects of a <italic>Mkx</italic> deficiency on PDL cellular heterogeneity and differences between gene expression in PDL tissues from wild-type (WT) (<italic>Mkx</italic><sup><italic>+/+</italic></sup>) and <italic>Mkx</italic> knockout (<italic>Mkx</italic><sup><italic>−/−</italic></sup>) rats using single-cell RNA sequencing. We identified 12 cell clusters comprising mesenchymal cells and macrophages. The expression of <italic>Mkx</italic> and scleraxis (<italic>Scx</italic>; another key transcription factor of PDL), was mutually exclusive, and partitioned mesenchymal cell clusters into <italic>Mkx</italic> and <italic>Scx</italic> types that dominantly expressed proteoglycans and elastic fibers, and type 1 and 3 collagen, respectively. Ossification-related genes were upregulated in mesenchymal cell and osteoblast clusters with more <italic>Mkx</italic><sup><italic>−/−</italic></sup> than <italic>Mkx</italic><sup><italic>+/+</italic></sup> PDLs. Increased number of cells and inflammatory mediators were observed in macrophage clusters of <italic>Mkx</italic><sup><italic>−/−</italic></sup> PDL. These results suggested that <italic>Mkx</italic> plays an important role in maintaining PDL homeostasis by regulating specific cell populations and gene expression.</p>